Experimenting with Front Alignment

[petek]

On cool days I drive my MINI Cooper S, a small car, 97" wheelbase, handles like a gocart. In fact, I like the handling of the Cooper better than the handling of my Cobra. The Cooper feels planted, the Cobra feels like it's on it's tippy-toes. (Yes, I know, the Cobra is never going to be a 2004-equivalent supercar, but I can certainly improve what I've got.)

So I got to thinking, what if I played around with the front end alignment on my Cobra. I've got a 94" wheelbase Classic Roadsters Cobra. Front end is Mustang II based. As everyone is aware, aligning a Mustang II based front suspension is a PITA.

After reviewing the postings here I've come up with a potential solution. Over at www.polepositionrp.com they've got an adjustable upper a-arm (picture below). These adjustable a-arms should allow me to make alignment adjustments with significantly greater ease.

Comments? Suggestions?

[Edbo]

The uppers supplied with FFR's are made by PP and similar to your pic, but with straight tubes instead of curved. Same Chrysler balljoints.
Mine are very easy to adjust. I use a Pole Position caster/camber gauge and have experimented extensivly with my FFR. Here's what suits me best, with a Flaming River 20:1 rack:
3 degrees positive caster, zero camber, 1/16" total toe in.

I ran 5 degrees caster for a while and it tracks down the highway solid but steering is quite heavy in turns.

Something that has a strong influence on cornering is 'wedge'. That's the corner-to-corner weight distribution. If you have a way to weigh each wheel wedge can be adjusted to near zero by adjusting spring preloads at the front end.

Here's a tip for you: Factory Five had a recall of those PP arms recently because of improper hardware supplied by PP. The 7/16" nuts supplied at the pivot points were not locknuts and there were numerous cases reported of the nuts falling off, unknown to the owners. Luckily, no one reported an accident because of it.

HTH, Ed

[Steve R]

Pete,
Too bad they did not make them with turnbuckes I.E. One side left hand thread, the other right hand (on each leg). This would make adjustments a snap. Maybe that is not possible given that config????
Steve

[Edbo]

Steve,
I don't know how the bent tube models work, but the FFR straight tube models are as you describe; left and right threads. You just turn the center section to adjust them.

Ed

[petek]

Steve, no kidding!

Ed, that's exactly what I want to do, experiment with settings to see what I like the best. I might even go as far as to replace the steering rack with a power rack just to see how I like that. (I understand that Flaming River has a speed-dependant power rack out now).

How do adjust caster with these A-arms, shim the mounts?

Thanks fellows.

Anyone else want to chime in?

[Steve R]

Pete,
I wouldn't $hit ya. You're my favorite turd!
(you DID ask for comments)
Seriously, changing the lenth of either leg will alter the caster.
Steve

[wilf leek]

Petek - forget playing with adjustable A arms. Just try dropping your front tyre pressures first. Alot cheaper.
Anything above 20 lbs makes my car feel "on tippy toes" too. 19lbs is perfect.

I bet tyre pressures would make a BIG difference to how it feels. just try it. How much can it cost?

[Ken Greene]

to check for proper tire pressure take some chaulk and make a couple big stripes across the width ofthe tread then take the car for a short run thnen come back and check the chaulk. if its rubbed off on the edges that means not enough pressure (prolly not the case) if its rubbed off in the center with it still showing on the edges its to much pressure (most likely the case). Then adjust the pressure acordingly until the chaulk rubs off evenly accross the tire. make sure to reapply the chaulkf before each run and make sure to make both left and right turns.

[kountzecobra]

The a-arms with straight tubes may not work on all MII front ends. The reason for the curved tubes is for clearance around the spring pockets.

[petek]

Steve, yeah, I checked and saw how the alignment works with the adjustable arms, simple enough, easy enough.

Wilfred - good idea, I've got the tires aired up pretty well now (25 lbs or so), I'll drop 'em 5 lbs and give it a try. Thanks ALOT.

Ken - great idea

David - the ones I'm looking at are D-shaped, look like they'll work much better than the A-shaped ones.

Thanks everyone, I'll let you know the results. Goin' to take some expementation and some time -- but isn't that the fun part anyway!

[petek]

Well Wilphy, I dropped the front tire pressure and discovered two things: the handling became a but "mushy" as expected. I'm really starting to think I should be playing around with the rear tire pressure instead of the front.

The second thing: the steering really doesn't "self-center" much at all ... which makes me wonder about the caster setting.

It's suppose to rain the next few days, I think I'll put the car up and check the alignment. Of course I haven't the foggiest idea what I'm doing, nothing like learning on the job!